20261209 has 4 divisors (see below), whose sum is σ = 20517760. Its totient is φ = 20004660.

The previous prime is 20261191. The next prime is 20261231. The reversal of 20261209 is 90216202.

It is a happy number.

20261209 is nontrivially palindromic in base 2.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20261209 - 2⁵ = 20261177 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20261209.

It is not an unprimeable number, because it can be changed into a prime (20261279) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 128157 + ... + 128314.

It is an arithmetic number, because the mean of its divisors is an integer number (5129440).

Almost surely, 2^20261209 is an apocalyptic number.

It is an amenable number.

20261209 is a deficient number, since it is larger than the sum of its proper divisors (256551).

20261209 is an equidigital number, since it uses as much as digits as its factorization.

20261209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 256550.

The product of its (nonzero) digits is 432, while the sum is 22.

The square root of 20261209 is about 4501.2452721441. The cubic root of 20261209 is about 272.6183712650.

The spelling of 20261209 in words is "twenty million, two hundred sixty-one thousand, two hundred nine".